The invention relates to the field of electric machinery and, more particularly, to apparatus and a method for processing operating data for an electric motor.
Apparatus and methods are known, for example, from the design of speed controls for electric motors that motor operating data may be continuously sensed as to, for example, the speed of rotation, angle of rotation, motor current and the like. The different types of data can be correlated with one another as well as with associated predetermined reference levels in order to determine what speed control signals might be required in a particular situation for transmission to motor speed control devices within the scope of this known processing, the actual operating motor data is only temporarily stored in data memory of a processing device, for example, for a few data cycles or for a very short duration as compared to the expected or actual service life of the electric motor controlled.
Large electric motors such as high-voltage motors represent high-value investments. Their long term availability for service, the economic efficiency of their capital-intensive installations, and the reliability of associated protection devices depends on the optimum planning of their replacement and their scheduled maintenance. Planning for maintenance and replacement should be accomplished dependent on the actual stress of the associated motor, instead of at rigid intervals normally selected based on an estimated nominal or maximum motor stress level.
To optimally choose a maintenance schedule or date of replacement, however, requires precise knowledge of the actual motor stress over an extended period if not the entire service life of the respective electric motor, but the data need only be recorded during its period of actual use, i.e. the knowledge of its actual life cycle. Biographic events of the motor, however, cannot be reconstructed from the known control devices and methods at least because of the, at most, brief storage of the operating data. Furthermore, such data processing should be relatively secure in the event of dispute between motor manufacturer and user over warranty or motor abuse issues.
Consequently, the problem posed by known devices and methods is that there is a need for a long term, yet secure processing of certain motor operating data. Compared with known speed control devices and methods, there is a far greater quantity of data involved, the data is related primarily to stress, and the data must be preserved for a much longer period of time.